More than 90% of the raw materials for today's chemical industry are petroleum feedstocks while only one-tenth of the feedstock comes from renewable resources. Considering the increasing importance of sustainability, there is interest on the development of fuels, chemicals and materials from renewable resources. The transformation of plant oils, due to their low cost, biodegradability and large scale availability, has received significant attention. In addition to large scale availability, a wide range of products can be obtained from plant oils which make them cost-effective and environment friendly alternative.
For chemical conversion and formation of new carbon-carbon double bonds, olefin metathesis is considered a versatile synthetic transformation tool and has been used in both pure and applied chemistry. Generally, olefin metathesis can be classified into ring-opening, ring closing and cross-metathesis. Metal-catalyzed olefin cross-metathesis (CM) has become a standard synthetic method with numerous industrial uses, including the well-known Shell Higher Olefin Process (SHOP). Olefin cross-metathesis is a catalytic reaction between two alkene molecules that results in redistribution of alkylidene groups. The cross-metathesis of an olefinic compound with ethylene is called ethenolysis, and a cross-metathesis with an olefin other than ethylene is called alkenolysis. Various efforts have been made on the conversion of plant oil derived fatty acids into products using ethylene metathesis (ethenolysis) chemistry. The production of olefins through ethenolysis may produce high value linear α-olefins which are direct antecedent to various applications including monomers for polymer synthesis, cosmetic ingredients, lubricants, detergents, soaps, perfumes, antimicrobial agents and renewable fuels.
Cross-metathesis of seed-oil derivatives and purified methyl oleate as a model substrate is known. However, these reactions are carried out in organic solvents and a high catalyst loading is required for effective conversion, which limits industrial scale viability of these processes, and particularly ethenolysis.
Purified methyl oleate has been used as a model substrate for metathesis. Relatively high turnover numbers (TONs) have been reported on the alkenolysis of methyl oleate using other olefins as ethylene surrogates in CM reactions. For example, the TON for CM of methyl oleate with propylene and 2-butene has achieved TONs as high as 192,900 and 470,000 respectively. However, metathesis with higher olefins results in the production of substantial amount of internal olefins, which are considered low value products compared to α-olefins produced through ethenolysis.
There remains a need in the art for methods of efficiently producing olefins from renewable fatty acid sources.